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Ishii, S., Kobe University, Kobe, Japan, shota070428@gmail.com
Uchiyama, Y., Kobe University, Kobe, Japan, uchiyama@harbor.kobe-u.ac.jp
Miyazawa, Y., JAMSTEC, Yokohama, Japan, miyazawa@jamstec.go.jp

A DOWNSCALING EXPERIMENT ON REPRODUCIBILITY OF THE KUROSHIO OFF JAPAN

Whereas the Kuroshio flowing up off the eastern side of Japan is known to be controlled by the mesoscale dynamics, effects of the submesoscale dynamics on the mean structure, eddies, frontal processes, stratification, etc. has not been fully understood. In prior to designing a submesoscale Kurhoshio modeling, a detailed numerical downscaling experiment is performed with ROMS at a horizontal resolution of 3 km, forced by the assimilative JCOPE2 at 1/10 deg. as the boundary condition. Three nesting configurations are prototyped for an assessment of surface kinetic energy: 1) a free run without any controls 2) with a homogeneous constant horizontal eddy viscosity of 100 m2/s, and 3) a three-dimensional T-S nudging towards the JCOPE2 at a nudging time scale of 20 days. Among the others, the T-S nudging is found to best reproduce the Koroshio including its paths, surface KE and EKE, thermocline slopes and stratification. In turn, the free run substantially overestimates the KE and EKE because of the lack of subgrid-scale energy dissipation associated with the submesoscale turbulence leading to overly meandered paths and more isolated warm/cold-core rings.

Oral presentation

Session #:GS04
Date: 7/09/2012
Time: 16:45